[JDEV] request for ideas: RFC822 to JID mapping

[David Waite]

Matthias Wimmer wrote:

> Hi David!
>
> David Waite wrote:
>
>> Not just that - JIDs can have longer nodes than email addresses (255 
>> bytes vs 64 bytes), and can have resources, a concept which doesn't 
>> map to 822/2822 addresses. 
>
>
> Yeah, but I think this is a minor problem as most people won't use 
> node with more then 64 bytes. BTW: I think nodes can have up to 256 
> bytes and I think it's strange to limit it based on bytes instead of 
> characters ... *g*)

Oh, it's more complicated than that. One character can be composed of 
multiple codepoints, which (in UTF-8 encoding) can be composed of 
multiple bytes. What you probably meant was codepoints, which is even a 
weirder place to stand than bytes - the computer has difficulty using 
fixed-length fields for the username, and clients still have to figure 
out how many characters can be represented based on the # of codepoints.

With the limit set for full characters, you have to understand and 
combine the bytes into unicode codepoints and then into full characters. 
This is a lot of work to be done on the server, since the server does 
not actually operate on the string lexically - it just wants to know if 
it is a valid address before routing against it. Also, this does 
penalize speakers in latin languages. e.g.

(A hopefully correct example)
1 word in US7ASCII could be 8 bytes , 8 codepoints and would be 8 
characters.
1 word in some asian languages could be 1 character, 3 codepoints and 12 
bytes.

The Chinese speaker has used 1/8th the # of characters as the English 
speaker, but has conveyed the same amount of information.

At least with bytes, its (computationally) easy for everyone to figure 
out what the limit is.

Finally - I think it would be interesting to be able to 'limit' a server 
to a subset of the full JID scheme with a server setting; perhaps a 
subset which corresponds with a subset of RFC 2822. I know I would 
probably turn this on just to guarantee that I can migrate the user 
information storage and authentication mechanisms around to systems 
which do not support unicode.

Finally RFC 2822 allows for quoted literals, and quotes are not legal in 
JIDs - so even declaring a subset you still would still not be able to 
get a 1:1 mapping without ammending  the JEP for JIDs. Since this is for 
allowing email to users on the jabber server, having the local JIDs as a 
subset of RFC2822 is fine.

-David Waite